Seat mounting hardware

[Rick from Fla]

I am replacing the carpet in my 1980 Avanti. all of the boats have to be cut out. does anyone know where I can get the nuts that mountain in the body or tell me how they work? any help would be appreciated. 

[Avanti83]

The nuts are bonded onto the fiberglass body. The front are threaded plates in the riser that mounts the front bolts and the same under the floor for the rear mounts. Replacing the front ones requires cutting slots in the riser and adding a plate with a threaded hole and using pop rivets to hold it. The opening can be reglassed.

If the bolts are still in the nuts just drill them out carefully and replace them.

One rear bolt can be reached from underneath but the other in obscured by the hog trough. It could be fixed by a rivet nut but that's not strong enough in my book. I'd probably open the floor enough to get a plate underneath with a threaded hole.

In my 74, I just wasn't happy with the OEM rear mounting points for strength when I upgraded the seats so I used the belt mounting holes in the frame and cross member.

You can see one of the original rear mounting holes just above in the floor. I just glassed over it before I installed the carpet.